This invention relates to a composite pipe and the manufacture thereof.
Flexible and rigid pipes are commonly used to transport various types of fluids or gases. The pipes comprise a plurality of materials joined together in various manners to form a conduit for advance of the fluid and/or gas materials therethrough.
The use of the extrusion process to form a pipe having multiple material layers is known. Various disadvantages with the extrusion process have arisen including the possibility of variances in the pipe thickness over the length of the pipe and radial/hoop expansion of the pipe during the manufacturing process. Such actions may cause internal deformities leading to leakage and/or burst during fluid and/or gas transport. Also, longitudinal movement between the material layers will cause abrasion therebetween resulting in premature wear and possible pipe failure. Moreover, in past pipes annuli and/or voids may appear between the pipe layers. If not properly vented, undesirable permeation of the gases of the transported fluid and/or gas into these areas may occur, which may lead to pipe failure.
In response thereto a coherent, multi-layer pipe is desired which avoids the above problems. A method of pipe manufacture is presented, which provides a coherent bond among the material layers so as to present a unitary mass of material with no voids therein as well as longitudinal or radial movement therebetween. The process is enhanced by the relationships of the melt temperatures of the material layers as well as a cooling of the extruded pipe core during the subsequent wrapping of intermediate reinforcing layers of a resinous prepreg or similar material. The melt temperature relationships and/or cooling precludes expansion and contraction of the pipe core. Thus the pipe core remains round without the appearance of undesirable annuli or voids between the material layers. Accordingly, the bonding presents a cohered multi-layer pipe, which has various desirable properties including chemical and pressure resistance, the preclusion of annuli and/or voids between material layers and resistance to lateral and radial layer movement.
It is therefore a general object of the invention to provide a versatile composite pipe and method of mass production manufacture for effectively transporting pressurized fluids or gases therethrough.
Another object of this invention is to provide a composite pipe and method of manufacture, as aforesaid, having a plurality of layered materials cohered into a unitary mass.
A further object of this invention is to provide a composite pipe and method of manufacture, as aforesaid, which precludes the appearances of voids and annuli between the material layers.
Still another object of this invention is to provide a composite pipe having a method of manufacture, as aforesaid, which precludes undesirable radial movement of the inner core during pipe manufacture and application of the material layers.
Another particular object of this invention is to provide a composite pipe, as aforesaid, having no free floating fibers within the pipe mass.
Still a further object of this invention is to provide a composite pipe, as aforesaid, which can be effectively butt fused in the field.
A particular object of this invention is to provide a composite pipe, as aforesaid, wherein the relationships of the melt temperatures among the pipe layers are chosen so as to be efficiently controlled to preclude deformities during pipe manufacture.
Other objects and advantages of this invention will become apparent from the following description taken in connection with the accompanying drawings, wherein is set forth by way of illustration and example, a now preferred embodiment of this invention.